The water body is characterized by the structure and concentration of elements in the boundary layer. The boundary layer formed at the bottom of a water body is labile in character (with an easily disturbable structure). It comprises much more substances and elements than can be found in the volume of the water body.
The instruments in use do not enable to sample the boundary layer in its original state in the bottom of a water body, because the penetration of the sampling tube into the sampling environment is accompanied by a smaller or greater shock. As a result, the boundary layer is crushed, pushed away from the sampling tube and does not get into it.
Still, it is possible to get samples from single macrocomponents (bottom vegetation, fauna, macroparticles of solid sediments).
To get a boundary layer sample with the least possible disturbance, an operable sampling device is needed, i.e. its movement and operations in the sampling environment should be adjustable.
Known is the device for taking samples from near-bottom water, water-saturated suspended mud and solid bottom sediments, the tube for sampling solid bottom deposits of which can be disassembled into separate sections (SU 1013810A1). To avoid the disturbance of bottom sediment structure on rapid penetration of the sampling tube into bottom sediments, the penetration speed is regulated by means of shock absorber unit (SU 1559261A1; U.S. Pat. No. 4,709,584; DE 3635748A1; FI 81413A). On taking near bottom water samples bathymeters are used, which are situated higher than the bottom sediment sampling tube and are in direct contact with the latter (U.S. Pat. No. 4,996,887; DE 3930300 A1). The closing mechanism of the lower opening of the sampling tube (SU 1597663A1; U.S. Pat. No. 5,062,309; DE 3931131 A1).
From the prior art is known a device for taking samples from the bottom boundary layer of a water body, which consists of the supporting frame with footings, the sampling tube disassemble into separate sections and the absorber units (EE9800130A).
Despite using the named above solutions, it is a drawback of such device when obtaining undisturbed samples that after a sample has been taken from the boundary layer the sectioning of the interior of the sampler's upper part (bathymeter) with valves helps to an extent avoid the mixing effect caused by oscillation and vibration due to waves and the flowing of the water (especially when the waves are high) when the device is lifted, but it has not been done in the lower part of the sampler that is foreseen for taking samples of solid bottom sediments and suspended mud.
Despite guidance, i.e. slow controlled lowering into the bottom layer of the body of water, sampler movement in the sampling environment may cause destruction of the initial structure of the sample, i.e. the mixing effect occurs due to friction (surface tension) between the inner wall of the sampling tube and the sampling environment. The degree of mixing depends on the distance of the sampling tube movement: the longer the way of sample movement in the sampling tube, the greater the mixing effect. Thus, the sample in the higher part of the sampling tube has been subject to a greater mixing effect than in the lower part. To obtain samples with the least possible disturbance, i.e. undisturbed samples, the sampling tube should have a minimal effect on the sampling medium.
In the water basins with a high organic matter inflow (shallow protected sea areas, eutrophied lakes, bog pools) a thick semiliquid suspended mud layer is formed. In the case of the known devices, the footings on the lower end of support rods of the shock absorber unit are not capable of retarding the descent of the device because their contact area is too small. The sampling tube penetrates at high speed into the sampling medium (near bottom water, suspended mud) and does not enable to get undisturbed samples from the boundary layer of a water body.